Molecular characterisation of two paralogous SPO11 homologues in Arabidopsis thaliana

The Spo11 protein of yeast has been found to be covalently bound to double- strand breaks in meiosis, demonstrating a unique role of the protein in the formation of these breaks. Homologues of the SPO11 gene have been found in various eukaryotes, indicating that the machinery involved in meiotic reco mbination is conserved in eukaryotes. Here we report on SPO11 homologues in plants. in contrast to what is known from other eukaryotes, Arabidopsis th aliana carries in its genome at least two SPO11 homologues, AtSPO11-1 and A tSPO11-2, Both genes are not more closely related to each other than to oth er eukaryotic SPO11 homologues, indicating that they did not arise via a re cent duplication event during higher plant evolution. For both genes three different polyadenylation sites were found. AtSPO11-1 is expressed not only in generative but also to a lesser extent in somatic tissues. We were able to detect in different organs various AtSPO11-1 cDNAs in which introns wer e differently spliced-a surprising phenomenon also reported for SPO11 homol ogues in mammals. In the case of AtSPO11-2 we found that the 3' end of the mRNA is overlapping with a mRNA produced by a gene located in inverse orien tation next to it. This points to a possible antisense regulation mechanism . Our findings hint to the intriguing possibility that, at feast for plants , Spell-like proteins might have more and possibly other biological functio ns than originally anticipated for yeast.